Editing Cosmological constant (section)

=== Equation of state ===
Another ratio that is used by scientists is the [[Equation of state (cosmology)|equation of state]], usually denoted {{mvar|w}}, which is the ratio of pressure that dark energy puts on the universe to the energy per unit volume.<ref>{{harvp|Brumfiel|2007|p=246}}.</ref> This ratio is {{nowrap|{{mvar|w}} {{=}} −1}} for the cosmological constant used in the Einstein equations; alternative time-varying forms of vacuum energy such as [[quintessence (physics)|quintessence]] generally use a different value. The value {{mvar|w}} = {{val|-1.028|0.032}}, measured by the Planck Collaboration (2018)<ref name="Planck-2018">{{harvp|The Planck Collaboration|2020}}.</ref> is consistent with {{val|-1}}, assuming {{mvar|w}} does not change over cosmic time.